The need for energy absorbing padding to cushion mechanical impact loads is present in many environments. For example, personal protection equipment such as helmets, shin guards and body part protectors typically include some form of cushioning layer. The type of helmet commonly used in football (i.e., American football), for example, has a hard outer shell that generally is molded of impact resistant plastic such as acrylonitrile butadiene styrene (ABS) or polycarbonate. The interior of the helmet is lined with various components that may be formed, for example, from various materials such as felt, fibrous knits, foam-padding material such as ethylene vinyl acetate, vinyl nitrile or urethane/rubber. Inflatable shaped air bladders are also commonly used in sports helmets. The liner is included in the design of the helmet and functions to provide some cushioning of direct physical head impacts during active play.
Presently, much research and development as well as medical studies are on-going on the effects sport action has on injurious head impact and Traumatic Brain Injury (TBI) including concussions. New sport helmet designs and helmet padding materials are constantly being investigated in the context of mitigating the effect of head impact occurrences and their severity in the contact sports. Along with this is the concept of employing sensors in these sport helmets (e.g., American Football) that would be able to detect sport injury impact “strike” or “hit” intensity and direction of impact.
Other environments where high impact forces are present are those involving body armor. For example, bulletproof vests typically are fabricated from polyaramid (Kevlar®), ultra high molecular weight polyolefin fibers, woven or mat fabrics having high impact and cut resistance. When struck by a projectile, these vests and similar clothing can impress a direct force on the wearer's body area that, while potentially life-saving, can cause significant bodily bruising and/or a bone fracturing injury if not properly cushioned against the body.
In practice, textile based spacer fabrics (by themselves) are presently considered to be breathable alternatives to Foam in Impact Energy (Helmet and Body pad) applications. For example, a product like DEFLEXION® is a textile structure type spacer fabric product that was being produced and marketed by Dow Corning Corp for ski-jacket padding. Also, Hong Kong Polytechnic University has been studying spacer fabrics for motorcycle helmet padding applications.
It is desirable in these and in other environments where impact forces are involved that the helmet or protective garment be comfortable and in some applications, that it has the ability to allow airflow between the user's body and the helmet or protective garment. It also is desirable to provide a liner construction adapted for use in such environments that is reasonably flexible, can be formed into various shapes, displays an energy absorbing compression function, can be worn close to the body and enables airflow between the body and the protective helmet or garment.
There is a need in sport and military helmet design to develop a helmet pad material device that would be able to detect and/or record and/or transmit signals that sense the intensity, location and duration of a mechanical “hit” to a helmet or protective body apparel. The concept of detecting and sensing mechanical impact strikes would also apply to biomedical sensors such as noncontact ECG sensors, respiratory sensors, sport and military body protection apparel systems. Polymeric body sensors have been described in “Wearable sensors;” Sarah Brady, et al., Studies in Health Technology and Informatics, Volume 117, pp 80-88 (2005).
A study of polyurethane rubber covers that have been applied to the outside of football helmets has been reported in “Retrospective report on the effectiveness of a polyurethane football helmet cover on the repeated occurrence of cerebral concussions,” by Torg, et. al., Am. J. Orthop (Belle Mead N.J.) 1999; 28(2):128-32.] In the 1990's, when these tests were carried out, it did not seem that football helmet covers provided any protection against recurring concussions. However, this study was tainted by uncertainties in the fact that the human subjects in the study had already suffered concussions. It is well known that athletes with a history of concussions are significantly more prone to new concussions than players with no previous history of concussions. However, this study has not curbed the idea of using football helmet covers in high school football practice sessions and other non-league scrimmages. There are presently at least two sporting goods companies, Champion and Guardian who presently have football helmet cover products on the market. In fact, many high school football programs have adopted using these helmet covers in practice. The overall use of such covers in actual competition has not yet caught on. In this context, there seems to be a potential opportunity for other means of accomplishing outside-the-helmet shell impact blunting technology.
It is desirable in these and in other environments where impact forces are involved that the helmet or protective garment be comfortable and in some applications, that the garment has the ability to allow airflow between the user's body and the helmet or protective garment. It also would be desirable to provide a liner construction adapted for use in such environments that is flexible, can be formed in various shapes, displays an energy absorbing compression function, can be worn close to the body and may enable airflow between the body and the protective helmet or garment. Traumatic Brain Injury (TBI) and concussion causing head strikes in sports, especially football and hockey, are a topic of great contemporary concern to the professional, collegiate, high school and other youth sports groups. Concern about long term health effects of head strikes has now reached dramatically high social and legal interest levels. Therefore, any ideas put forth on ways of mitigating damaging head injuries in sports are welcome to all of society and especially the sports industry. In all sport helmet designs, fabrications and structures, the inside of the helmet is almost always fitted with energy absorbing pads, foam, air bladders, felt and other fibrous materials such as spacer fabric textile structures.
There are some conventional systems that use flocked fibers on the outside of sport helmets for horse riding and polo sports. However, flocked polo helmets are mainly for aesthetic effect; outside of helmet flocking with black fibers results in a non-glare, light absorbing, non-reflecting helmet surface. Also, some of these riding helmets use simple single side flocked inner linings to provide some against-the-head comfort. However in this case there is no mention of the helmet's impact energy absorbing capability. Furthermore, these flocked polo helmets do not indicate they have the proper type of flock material or coating configuration that will be needed for impact energy absorption. It is noted that in the equestrian sports, the issue of head injury is also important.
Currently, head protection in American football is in the form of a shaped, hard/tough molded plastic helmet whose interior is fitted with energy absorbing pads and the like. In this scenario, an impact strike (e. g. helmet-to-helmet) will first hit the hard plastic helmet shell—this kinetic energy will then be transferred to the inside positioned helmet pads which are there to absorb energy before in reaches the wearer's head. These interior pads function to lower the impact energy of this outside-the-helmet hit to a minimum level. This hit-to-the-head is presently blunted by only the interior helmet pad system. Since the hard plastic helmet material does not absorb much of a hit's kinetic energy, it is the helmet's interior pad system that is responsible for absorbing most of this impact energy. In fact the hard plastic helmet can sometimes serve as a conduit for spreading a strike's impact energy throughout the whole helmet.